guys can i open up my inlet port width side to side to 22mm? the std port is only 20.4mm. i just want to make sure i will not screw something up. buy doing this i hope to gain more incoming volume mix for more revs. the engine is a 29.5 zenoah.
i was told not to do it because i will slow down the speed of the incoming mix and create a lazy motor with no bottom torque. i always clean mine up to around 21mm but want to try 22m. ant feedback will be welcome.
thanks
john

The intake port is the main restriction in a Zenoah. Widening it will help, but it really needs more intake timing. The easy way to do this is by cutting the intake side piston skirt. If you go too far, you only need to replace the piston. This needs to be matched with increased exhaust timing as well. I've taken around .040" off the skirt depending on the amount taken off the cylinder base to lower the squish clearance.

Lohring Miller

thanks for the reply lohring. what amaze me is that the 25.4 and 28.5 zen got the same inlet port size. why didn't zenoah thought of making it bigger as it is a larger cc motor? i measure my t.k port and it is huge compare to the zen, 23.45mm t.k port and zen 20.4mm. so if i should open up the inlet port my 29.5 can perform better.